The thickness of the velocity boundary layer is normally defined as the distance from the solid body to the point at which the viscous flow velocity is 99% of the freestream velocity (the surface velocity of an inviscid flow).

What is the value of thickness of boundary layer?

What is the value of the thickness of the boundary layer at leading edge of the plate? Explanation: The thickness of the boundary layer is variable along the flow direction.

How thick is the boundary layer on a wing?

The boundary layer isn't very deep, maybe . 02 to an inch thick, but it's important. It's the source of skin friction drag, and can actually decrease pressure drag. Air flowing in the boundary layer travels in one of two states: laminar flow and turbulent flow.